omnia_hw_ctrl

When newer GD32 application firmware jumps into original bootloader
firmware, the bootloader firmware gets stuck in exception. This is
because newer firmware enables some interrupts which the original
bootloader firmware does not disable before enabling interrupt flag.

Disabling all NVIC interrupts before going to other program solves this
issue.

Signed-off-by: Marek Behún <kabel@kernel.org>